Potterton Derwent Compact Plus Instruction manual

MAY 2004

Index
Section 1 Page
Fig 1 General Data and Dimensions 1
Table 1 Boiler Dimensions 1
Table 2 Connections 1
Table 3 Technical Data 2
Fig 2 Steel Base Strip Details 3
Clearances 3
Section 2
General 4
Optional Extras 4
Installation 4
Boiler Siting and Base 5
Section 3
Ventilation 6
- flue 6
- flue Size Considerations 6
- horizontal Flue Runs 6
- common Flue Systems 6
Water Circulation Systems 6
Boiler Protection 7
System Water Quality 7
- existing Systems 7
- new Systems 7
Sealed Systems 7
- noise level 7
Section 4
Boiler Installation 8
- risk Assessment 8
- manual Handling 8
- personal Protective Equipment 8
- confined Spaces 8
- electrical Safety 8
- preparation 8
COSHH 8
Customer Check List 9
Unpacking Boiler 9
Boiler Main Components 9
Control and Safety Equipment 10
Working Principles 10
Hydraulic Test of Boiler 10
- connecting the Water System 10
- condensate 10
- connecting the Electrical
Supply 10
- connecting the Flue 11
- connecting the Gas Supply 11
- boiler Controls 11
Section 5
Potterton Commercial Customer
Commissioning Check List 12
- contravention of
regulations 12
- commissioning 12
Page
Control Panel 13
Gas Assembly 14
Set Up 14
Adjusting the Air 14
Low Load Control & Set Up 15
Important Safety 15
Emergency Instructions 15
Addition Checks 16
Pre-Lighting 16
Commissioning Live Run 16
Ionisation Current Check 17
Ventilation Checks 17
Operation of Ancillary Controls 17
Boiler Maintenance 17
Boiler Cleanin 18-19
Water Flow Swtich 20
Fault Finding 20-22
- overheat operation 20
- burner lockout 20
- general arrangement of pilot
burner 20
Section 6
Wiring Diagram 23-24
Section 7
Spare Parts Lists 25-34

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 1
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS – CONDENSING PAGE 1
Fig 1 – General Data and Dimensions
Table 1 – Boiler Dimensions
Size A B C D E ØF G H I Return Flow
4456 1200 1050 1150 1130 182 157 81 87 1 ¼” 1 ¼”
6537 1200 1050 1194 1140 202 197 45 51 1 ½” 1 ½”
8699 1390 1255 1194 1140 252 283 45 51 1 ½” 1 ½”
B
C
Flow
Return
1400
G
ØF
263 I
874
H
868
DA
E
1300
143
243
1004
Ø34
931
60 485
Gas
Condensate
Note:
Maximum Working Temp 90°C
Maximum Working Pressure 3 Bar
Electrical Supply 230V 50Hz
468
Water 1 ¼” 1 ½” 1 ½”
Drain ½”
Gas 1 ¼”
Table 2 - Connections

SECTION 1 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 2 DERWENT COMPACT PLUS – CONDENSING
Table 3 – Technical Data
Model: Derwent Compact Plus Condensing 4/55 6/90 8/125
Number of Sections 4 6 8
CE Certification Number 0063B03166
Gas Category I2H
Nominal Heat Input 100% kW 54 90 125
Nominal Heat Input 80% kW 43.2 72 100
Nominal Heat Output 100% load 60/80°C kW 51.4 85.9 118.6
Nominal Heat Output 100% load 30/50°C kW 55.5 92.5 127.9
Nominal Heat Output 80% load 60/80°C kW 41 69 95
Nominal Heat Output 80% load 30/50°C kW 45.3 75.7 104.4
Fuel Consumption 100% load (NG) m³/hr 5.7 9.5 13.2
Fuel Consumption 80% load (NG) m³/hr 4.6 7.6 10.6
Nominal Gas Inlet Pressure (NG) mbar 20
Burner Manifold Pressure 100% (NG) mbar 16.5
Burner Manifold Pressure 80% (NG) mbar 10.5
Burner Injector Size (NG) mm 3.2
Maximum Design Pressure bar 3
Minimum Operating Pressure bar 0.5 (0.1 available on request)
CO2 NG 100% load %7.5 to 8.5 6.5 to 7.5 7.5 to 8.5
CO2 NG 80% load %6.5 to 7.5 6.5 to 7.5 6.5 to 7.5
Nominal Flue Connection Size Ømm 180 200 250
Flue Gas Volume m³/hr 95 175 235
Flue Draught Requirements mm 0-5
Flue Gas Temperature 60/80°C (100%) °C 63 73 80
Flue Gas Temperature 30/50°C (100%) °C 45 57 65
High Level Natural Ventilation to BS6644 cm² 270 337.5 416.25
Low Level Natural Ventilation to BS6644 cm² 540 675 832.5
Mechanical Inlet to BS6644 m³/sec 0.059 0.099 1.375
Water Flow Rate at 11°C ∆T at 100% lit/sec 1.21 2.01 2.78
Min Water Flow Rate at 20°C ∆T at 100% lit/sec 0.66 1.11 1.53
Hydraulic Resistance at 11°C ∆T kpa 30.6 48.97 66.32
Cold Feed Size to BS6644 or BS5440
Minimum Bore
mm 19 25
Safety Valve Size to BSS6644 or BS5440
Minimum Bore
mm 25 32
Safety Valve Size to BS6644 or BS5440
Nominal Size
mm 19
Maximum Flow Temperature °C 90
Minimum Return Temperature °C 30
Air Pressure Switch 100% Pa 50-64 400-427 400-427
Air Pressure Switch 80% Pa 20-34 150-174 150-174
Dry Weight Kg 252 345 437
Water Content Lit 28.3 39 54.3
Power Requirements 230V 50Hz 1Ph – Isolator and 6.3A Fuse
Required

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 1
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS – CONDENSING PAGE 3
Fig- 2 – Steel Base Strip Details – (see section 2 – Boiler Siting and Base)
The boiler feet MUST NEVER be fixed in position (this is to allow for expansion).
Sections 468
G mm 171 324 486
CLEARANCES
The minimum boiler room clearances for access, erection and maintenance are as follows: -
REAR - 500mm from rear of flue hood
SIDES - 10mm
FRONT - 700mm (to allow for burner removal)
TOP - 1000mm (to allow for cleaning)
Flammable products should never be stored in the space around the boiler. Any walls that are sensitive to heat
should be protected by an appropriate insulation.
G
485
710
Centre Line
Of Boiler
75
FRONT OF BOILER

SECTION 2 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 4 DERWENT COMPACT PLUS - CONDENSING
GENERAL
This boiler is NOT SUITABLE for installation in a
normally occupied area (i.e. kitchen).
A LIFETIME GUARANTEE is available on this boiler,
please refer to our standard terms and conditions for
details.
The Potterton Derwent Compact Plus Condensing
cast iron sectional boiler is available in three sizes.
Table 3 (page 2) gives kW outputs and technical data
for each model. The boilers work on 2 stages, 100%
and 80% of nominal output. They are approved to 3
Star efficiency and have Class 5 NOx.
The Derwent Compact Plus Condensing is suitable for
use on fully pumped open vented systems or a sealed
system with a maximum design pressure of 3 bar.
These boilers are delivered fully assembled on one
pallet with burner, flue hood, gas train, control panel
and case fitted.
For sites with restricted access the boiler block, with
drain off cock removed, will pass through a 660 mm
doorway.
If necessary the boiler block can be easily stripped
down into individual sections. (For section weights see
page 2) Our service office can offer this facility.
All boilers have the gas inlet on the left hand side.
The boiler sections are constructed with BS 1452
grade 220 cast iron heat exchanger manufactured in
accordance with EN 303.1.
The boiler has a control system, which incorporates
full safety features, which includes control and high
limit thermostats, thermometer and burner on/off
switch. All models have automatic ignition with a
sequential control box and an ionisation flame failure
device fitted to an interrupted 400W pilot burner.
The boiler sections are insulated by 25mm glass fibre
insulation to front and rear and 50mm glass fibre
insulation on the sides and top. The case is finished in
a powder coat paint.
RED – RAL 3001
GREY – (Non standard but closest match RAL 7024)
OPTIONAL EXTRAS
•Sequence control
•Low Head Kit
•Balancing Kit
It is recommended that the Potterton Commercial
Division’s trained engineers should carry out
commissioning, as this will make the LIFETIME
GUARANTEE valid.
INSTALLATION
The boiler should be installed in a clean boiler house
free of dust and corrosive vapours. During insulation
of system pipework and heavy building construction
work around the boiler, the boiler has to be switched
off to avoid damage.
Before starting work a risk assessment should be
carried out in the boiler house and its access to
ensure a safe installation and working environment.
Any person installing or working on the boiler must be
qualified and attention is drawn to the mandatory
requirements of CORGI. (ACOPS 16) registration for
all Gas Installers. They must also be electrically
competent and adhere to IEE regulations.
Manual Handling:-. Any person or persons moving or
lifting the boiler or any part thereof should be trained
in manual handling techniques and if necessary use
suitable lifting equipment to reduce the risk of injury to
themselves or other people.
The installation should comply with relevant British
Standard Specifications, Codes of Practice and
current Building Regulations, together with any special
regional requirements of the Local Authorities, Gas
Undertaking and Insurance Company. All electrical
wiring must comply with IEE. Regulations for the
Electrical Equipment of Buildings.
The installation of the boiler must be in accordance
with the relevant requirements of:-
Health & Safety at Work Act 1974.
Building Regulations 1991
Electricity at work Regulations 1989
Management of H&S at Work Regulations 1992
Manual Handling Regulations 1992
Model Water By-Laws 1986
Gas Appliance Directive: 90/396/CEE
Boiler Efficiency Directive: 92/42
Boiler Pressure Directive: 97/23/CEE
Low Voltage Directive: EN 50165
Other Standards: EN297 – EN656 – EN437 – EN677
BS 7671: 1992 - Requirements for Electrical
Installations, IEE Wiring Regulations 16th Edition.

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 2
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS – CONDENSING PAGE 5
BS 5440: 1990: Part 1 – Specification for Installation
of Flues
BS 5440: 2000: Part 2 – Specification for Installation
of Ventilation for Gas Appliances
BS 6644: 1991 – Installation of Gas Fired Hot Water
Boilers for Inputs Between 60 kW and 2MW
BS 7074: 1989: Part 2 – Application Selection &
Installation of Expansion Vessels & Ancillary
Equipment for Sealed Water Systems
BS 6880: 1988 – Codes of Practice for Low
Temperature Hot Water Systems
BS 779: 1989 – Cast Iron Boilers for Central Heating
& Indirect Hot Water Supply (Rated Output 44 kW and
Above)
CP342:2 – Centralised Hot Water Supply
Gas Safety (Installation & Use) Regulations 1998
IM/11 Flues for Commercial and Industrial Gas Fired
Boilers and Air Heaters.
IGE/UP/1 – Soundness Testing & Purging Procedure
for Non-Domestic Installations
IGE/UP/2 – Gas Installation Pipework, Boosters &
Compressors for Industrial & Commercial Premises.
Manufacturer's notes must not be taken in any way as
overriding statutory obligations.
BOILER SITING AND BASE
The boiler should be sited in accordance with BS
6644: 1991 with respect to protecting the boiler from
damage, air for combustion and ventilation, discharge
of products of combustion, clearances for service and
access, temperatures, noise levels, the disposal of
boiler water and the effects of flooding of the boiler
house or seepage from a roof top boiler house. See
page 4 for required boiler clearances for service and
access.
A level non-combustible floor capable of supporting
the weight of the boiler filled with water, see Table 3
together with any additional weight bearing down on
the base from connections, etc, must be provided.
The Derwent Compact Plus Condensing is designed
to be installed directly on the boiler house floor
provided it is adequate but we would recommend that
a base of adequate height off the floor so as to be
raised in case of flooding, but also low enough to
allow ease of erection is used. This should typically be
a 50mm concrete plinth with an area equal to that of
the plan of the boiler.
Heating systems must be installed so that water
cannot be returned from the heating system to the
drinking water system to which it is connected to
prevent the drinking water being contaminated by the
heating water or chemicals used in the heating water.
Consideration should be given to fitting steel strips
beneath the boiler feet for boiler base protection, see
Fig. 2 for base details.
When preparing a site reference should be made to
Local Authorities and Building Regulations 1991.
Before any work takes place a Risk Assessment
should be carried out to determine what possible risks
are associated with the work which is taking place.

SECTION 3 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 6 DERWENT COMPACT PLUS - CONDENSING
VENTILATION
Safe, efficient and trouble free operation of
conventionally flued boilers is vitally dependent on
the provision of an adequate supply of fresh air to the
room in which the appliance is installed. Account
must also be taken of any other fuel burning
appliance existing or to be fitted when designing the
ventilation and combustion air systems.
IMPORTANT: the use of an extractor fan in the same
room as the boiler (or in an adjacent room in
communication) can in certain conditions adversely
effect the safe operation of the boiler and therefore
must be avoided.
Further guidance on ventilation for gas appliances is
provided by BS 6644: 1991 and BS 5440 1989 Part
2.
FLUE
To ensure safe and satisfactory operation the
chimney system, which may be individual or common
in the case of modular boiler installations, shall be
capable of the complete evacuation of combustion
products at all times. The effective height of the
chimney terminal(s) above the boiler(s) flue outlet(s)
shall ensure sufficient buoyancy to overcome the
resistance of the bends, tees and runs of the flue
pipe involved and shall terminate in a down draught
free zone. The number of bends used should be kept
to a minimum and runs of flue pipe less than 45° to
the horizontal should be avoided in order to comply
with the recommendations made in BS 6644: 1991
and British Gas publication IM/11 "Flues for
Commercial and Industrial Gas Fired Boilers and Air
Heaters". The third edition of the 1956 Clean Air Act
Memorandum and the Building Regulations should
be strictly observed and approval obtained where
applicable, combustion chamber details are given in
Section 1.
The flue system must be designed to work
specifically to remove the products of combustion.
IMPORTANT: 90° square bends must not be used on
the flue system, including the boiler flue spigot, a
straight length followed by an "easy sweep" or lobster
back bend should be used.
FLUE SIZE CONSIDERATIONS
Nominal flue connection sizes are given in technical
data Table 3, these sizes refer to the boiler flue
connection spigot.
The actual size of the flue system will depend on
individual site applications. Below are general
considerations on sizing flue systems. These notes
are for guidance only and Potterton Commercial
Division cannot accept responsibility for any flue
system designs.
Horizontal Flue Runs
Horizontal flue runs are not recommended
particularly over 3m in length, where these are
unavoidable, advice should be sought from a flue
system specialist.
Common Flue Systems
Where multiple boilers are installed on a common
flue system then the flue system should be designed
to ensure the correct operation of the flue on varying
load conditions. In particular that the appliance flue
draught is within the operating parameter under full
load and partial load conditions. For safe and reliable
operation of the boiler plant it is recommended that
the variance in flue draught available at each
appliance under full and part load operation is
designed to a minimum.
(It is essential that the services of a specialist flue
system manufacturer are sought for the design of
common flue systems).
For further information regarding ventilation and
flueing see Potterton Technical Bulletin No.4, current
issue or see relevant British Standard publication
BS6644: 1991.
THE ABOVE RECOMMENDATIONS ARE FOR
GENERAL GUIDANCE ONLY. POTTERTON
COMMERCIAL DIVISION CANNOT ACCEPT
RESPONSIBILITY FOR FLUE SYSTEM DESIGNS
BASED ON THE ABOVE RECOMMENDATIONS.
WATER CIRCULATION SYSTEMS
The water circulation system should be indirect and
installed in accordance with the relevant parts of
British Standards Codes of Practice CP342.2 and BS
6644: 1991.
The maximum and minimum design temperature
differential across the boiler should be 20°C and
10°C and the boiler should be prevented from
operating with flow rates giving a temperature
difference across the boiler greater than 20°C based
on the full boiler output. Boilers operating under
constant flow conditions can be more accurately
controlled and are not subject to excessive
temperature stresses.

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 3
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS - CONDENSING PAGE 7
The boilers MUST NOT be fired under any
circumstances with less than the minimum water
flow.
On systems with variable flow rates due to flow
reducing devices, ie. TRVs, zone valves, etc, or
where the minimum heat demand, ie. summer
domestic hot water load, does not achieve the
minimum boiler flow rate then consideration shall be
given to incorporating a primary loop system. For
further information see Potterton Publication
Technical Bulletin No.1 Issue 2.
It is recommended that the system is designed to
give a constant flow rate. For further information on
water circulation systems see Potterton publication
Technical Bulletin No.1 and Technical Bulletin No.3
current issue.
BOILER PROTECTION
The provision of pump overrun by a time delay relay
or a thermostat situated in the flow pipe close to the
boiler is essential to remove residual heat from the
boiler.
The boiler and system should be protected by
suitable frost thermostats.
Never fill a hot boiler with cold water. Sudden
cooling may cause the cast iron to fracture under
the stress.
Unions and isolating valves should be fitted to the
flow and return manifolds so that the boiler can be
isolated from the system if the need arises.
SYSTEM WATER QUALITY
Boiler systems require the system water to be
controlled by the use of inhibitors to maintain a
neutral pH and inhibit corrosion. The system pH
should be controlled between 7 and 8. On systems
with Aluminium components a pH above 8.4 can
cause failure of the Aluminium. The water system
must be free of leaks to prevent raw water make up,
which will dilute any inhibitors, promote corrosion and
form lime scale.
The system water should be checked as part of a
maintenance programme as a minimum on an annual
basis to ensure that corrosion inhibitors and pH are
adequate for continued protection.
Existing Systems
On existing systems where boilers are being replaced
due to failure then the cause should be investigated
before installing new boilers. This can normally be
achieved by cutting open a failed boiler section and
examination for system debris or contamination.
Lime scale is a positive indicator of continuous
system water make up due to water loss. Evidence of
magnetite (black sludge) in the system and the
formation of gas in radiators causing air locking is a
positive indicator of corrosion.
Where an old system shows evidence of
contamination then system cleaning should be
carried out before installation of new boilers. The
heating system should be chemically flushed to
remove any lime scale or corrosion and a corrosion
and lime scale inhibitor added. Lime scale descalers
if incorrectly used could cause any remaining system
debris to continue to breakdown and contaminate the
new boiler causing boiler failure.
Advice on system cleaning and suitable products
should be sought from specialist suppliers of system
cleaners such as Fernox or Sentinel.
It is important to note that corrosion inhibitor can only
be used in an attempt to prevent corrosion from
occurring, where a system has an existing corrosion
problem, inhibitors will be ineffective and the system
requires cleaning.
On existing systems where comprehensive descaling
and desludging cannot be carried out then
consideration should be given to separating the new
boiler system from the existing system pipe work by
the use of plate heat exchangers.
New Systems
New pipe work systems should be thoroughly flushed
with a suitable cleaning agent to remove debris and
flux residues before filling. The system water should
be dosed with a suitable corrosion and lime scale
inhibitor.
SEALED SYSTEMS
General
Potterton Commercial boilers are suitable for use on
sealed systems designed in accordance with BS
6644: 1991 and BS 6880 Part 2. In addition,
reference should be made to the Health & Safety
Executive guidance note PM5 "Automatically
Controlled Steam & Hot Water Boilers".
Noise Level
Derwent Compact Plus Condensing boilers are
regarded as being ‘commercially quiet’, ie < NR63
under typical operating conditions.

SECTION 4 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 8 DERWENT COMPACT PLUS - CONDENSING
BOILER INSTALLATION
A Lifetime Guarantee is available on this boiler when
the Potterton Commercial Service Department carries
out Commissioning and the system meets with our
recommendations. Please refer to our Standard
Terms and Conditions for further details.
Risk Assessment
Before starting work a risk assessment should be
carried out in the boiler house and its access to
determine and ensure a safe installation and working
environment.
Regardless of the type of activity being assessed, the
principles of risk assessments are the same. The
basic steps are: -
•Classify Activity
•Identify Hazards
•Identify Existing Control Measures
•Determine Risk
•Assess Acceptability of Risk
•Prepare a Control Plan
•Implement Plan
•Review Plan
•Record Results
Manual Handling
Any person or persons moving or lifting the boiler or
any part of the boiler, should be trained in Manual
Handling Techniques and if necessary use suitable
lifting equipment to reduce the risk of injury to
themselves and other people.
Personal Protective Equipment
When undertaken any work you must comply with the
Personal Protective Equipment Regulations 1992.
Confined Spaces
A “confined space” as defined in the Health and
Safety Confined Spaces Regulations 1997 ‘ means
any place, including any chamber, tank, vat, silo, pit,
trench, pipe, sewer, flue, well or other similar space in
which, by virtue of its enclosed nature, there arises a
reasonably foreseeable specified risk.
Precautions should be taken in all areas where, by
virtue of its even partially enclosed nature, pose a
reasonably foreseeable specified risk.
Electrical Safety
Working on appliances can be broken down to two
main systems of work.
1 Safe systems of work are adapted for all boiler
maintenance & repair work undertaken on site.
2 The work undertaken does not affect the electrical
safety of the appliance. In particular the earth
connected to the buildings fixed electrical
installation.
In the case of (1) above electrical work should only be
undertaken once the boiler has been isolated from the
electricity supply and confirmed electrically dead. If
this is impractical then suitable precautions must be
undertaken to prevent injury.
In the case of (2) above checks are specified to
identify any abnormality in the electricity supply to the
boiler as well as to confirm that the boiler electrical
connections are reinstated correctly where it is
necessary to disconnect or reconnect any internal
wiring within the boiler.
If it is necessary to disconnect and reconnect the
appliance from the site electrical installation other than
means of a plug and socket then additional checks
shall be undertaken by an approved engineer to check
the earth loop impedance in accordance with IEE
regulations.
Always carry out preliminary electrical safety checks.
All appliances and central heating systems must be
provided with their own means of isolation for safety
purposes especially during installation and
maintenance.
Preparation
Preparatory to installation of the boiler a check must
be made to ensure that suitable facilities are available
for off-loading the boiler and moving it into it final
position ensuring all Manual Handling Techniques are
followed. Particular attention must be paid to ensuring
cleanliness of the boiler room.
COSHH
During the erection procedure there are a number of
items which are subject to the Control Of Substances
Hazardous to Health (COSHH) Regulations, and may
require specialist Personal Protective Equipment
(PPE) beyond what is normally required. Listed below
are the items subject to the COSHH Regulations and
the recommended precautions that should be taken.
For a full breakdown of any substances listed below,
please contact the Commercial Technical Department.
1 Refractory Ceramic Fibre Insulation –
Wear gloves, overalls and safety glasses. In the
case of an irritation rinse the affected area with

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 4
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS – CONDENSING PAGE 9
water and wash gently, in the case of eye contact,
flush abundantly with water, if irritation persists
seek medical advice.
2 High Temperature Glass Fibre Insulation –
Wear gloves, overalls and safety glasses. In the
case of an irritation rinse the affected area with
water and wash gently, in the case of eye contact,
flush abundantly with water, if irritation persists
seek medical advice.
3 Adhesive – Wear gloves, overalls. In the case of
an irritation rinse the affected area with water and
wash gently, in the case of eye contact, flush
abundantly with water, and if irritation persists
seek medical advice. Inhalation – continued
exposure should be prevented.
4 Sealing Rope - Wear gloves, overalls. In the case
of an irritation rinse the affected area with water
and wash gently, in the case of eye contact, flush
abundantly with water, and if irritation persists
seek medical advice.
Potterton Commercial Customer Check List
The items listed below have been put together as a
guide to actions that should be completed before the
erection/assembly of a boiler takes place.
1 Site access available for persons carrying out the
proposed work.
2 Site Managers/Personnel aware that work will be
taking place.
3 Risk Assessments carried out on possible risks
which may effect the persons carrying out the
proposed work.
4 When boilers are to be stripped and rebuilt, labour
and transport should be provided for moving the
sections from the delivery point to the final
erection point. If this is unable to be provided
notice prior to attending site should be given.
5 Sections/casing etc, should be kept in a clean and
dry area prior to erection/assembly.
6 Water should be available.
7 A drain off area should be available.
8 Power should be available.
9 A site representative should be available at all
times.
10 Clear instructions supplied to the persons carrying
out the proposed work regarding positioning the
boiler.
11 Fire evacuation procedures, facilities availability,
specific Health & Safety information, etc, should
be provided.
Items 7 to 10 are essential if boilers require pressure
testing.
UNPACKING BOILER
For all boiler sizes remove the wooden box, shrink
wrap polythene and the cardboard protecting the
boiler. The boiler block is held to the pallet by fixing
brackets on the iron feet.
Before removing the boiler from the pallet a risk
assessment should be carried out to ensure safe
removal. This should take into account that any
person or persons moving or lifting boilers or any
part there of should be trained in manual handling
techniques and if necessary use suitable lifting
equipment to reduce the risk of injury to
themselves or other people.
When moving the boiler block into position the
burner assembly should be removed if there is
any likelihood of damage occurring.
Jacks and crowbars should not be used against
the flow and return manifolds.
Boiler Main Components
The boiler is composed of the following main
components:
1. Gas Valve assembly including intermittent pilot.
2. Low NOx burner bars.
3. Primary Heat Exchanger (Cast Iron).
4. Pipework assembly connection between primary
and secondary heat exchangers.
5. Secondary Heat Exchanger (Stainless Steel).
6. Damper for air flow control.
7. Fan.
8. Air pressure switches.
9. Hydraulic assembly for water flow distribution in
the secondary heat exchanger.
10. Control & Safety Equipment.
11. Set-up components.

SECTION 4 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 10 DERWENT COMPACT PLUS - CONDENSING
Control & Safety Equipment
1. Low Gas Pressure Switch
2. Control Box Dungs
3. Air Pressure Switches
4. Overheat Thermostat
5. Secondary Heat Exchanger Overheat Thermostat
6. Combustion Chamber Overheat Thermostat
Set-up components
1. Damper for air flow control at 100% load
2. Rheostat for air flow control at 80% load
3. Control Board
Working Principles of the Derwent Compact Plus
Condensing
The boiler has been designed to work as a two stage
High/Low boiler. Full load (100%) for second stage
and low fire (80%) for first stage. The firing of the
boiler works to the following operation:
1. Pre-purge takes place for a duration of 40
seconds during which the pressure switches are
tested. If the pressure switch for the second stage
is not satisfied, but the first stage is satisfied, the
cycle will go to the next step.
2. Pilot lights during the next 10 second period.
3. Main burner establishes and cross lighting takes
place. The boiler will remain for 60 seconds on
first stage operation, even if the second stage
thermostat is calling for heat. The main valve
contains a regulator which is in charge of first
stage operation.
4. The boiler moves from the first stage operation to
the second stage operation (Nominal load) and
remaining on this setting until the thermostat is
satisfied. The main valve with its regulator ensure
the second stage operates correctly.
HYDRAULIC TEST OF BOILER
This is to be carried out on boilers assembled on site
or where water manifolds have been disturbed.
Fit a hydraulic test pump to the return manifold and fit
a valve to vent air from the flow connection.
Fill the boiler with cold water and, in accordance with
BS 779: 1976, pressurise up to 1.5 times the design
pressure, ie. 4.5 bar maximum, and observe for 30
minutes.
Connecting the Water System
The flow and return connections should be made to
the appropriate manifolds following the
recommendations of CP342 and PM5.
It is essential that all pipework connections to the
boiler are self-supporting, correctly aligned and allow
for free expansion of both boiler and pipework.
Care should be taken in the pipework design to
prevent strain on the connections. Excessive strain
can leak to premature failure of the boiler, which is
obviously outside the terms of our warranty.
The use of expansion bellows to take up both axial
and lateral movement is recommended.
The flow and return connections are made at the rear
of the boiler.
Condensate
The condensate siphon of the secondary heat
exchanger is at the rear of the boiler. It is only
permissible to drain the condensate directly into a
domestic sewer system when the system consists of
corrosion-resistant materials (e.g. PP pipe, stoneware

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 4
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS – CONDENSING PAGE 11
etc.). It must be possible for the condensate to drain
freely into a funnel. A trap must be installed between
the funnel and sewer system.
Connecting the Electrical Supply
The electrical supply should be 230V 1Ph 50Hz. A
6.3A fuse and a suitable two pole isolator having a
contact separation of at least 3mm in all poles has to
be provided by the installer for isolation of the boiler.
All on site wiring shall conform to IEE Regulations.
The live and neutral connections should be made to
the control panel terminal block. The earth connection
should be made 50mm longer. The length of the
conductors between the cord anchorage and the
terminals must be such that the current carrying
conductors become taut before the earth conductor if
the cable or cord slips out of the cord anchorage. The
wiring diagrams are included in this manual and also
on the door panel of the boiler.
For multiple boiler installations each boiler shall have
an isolator and fuse as detailed above to protect the
boiler and allow for maintenance.
Connecting the Flue
The fluehood has a vertical female outlet into which
the flue should be fitted and sealed fitted (dimensions
given in General Data). It is recommended that a
single skin stainless steel fully sealed flue system be
installed and the flue is suitable for condensing
boilers.
Connecting the Gas Supply
The connection should be made to the male
connection (size given in Table 2). A union and
isolating valve should be fitted close to the boiler to
allow disconnection of the boiler controls for
maintenance and repair.
The gas supply should be made through a suitable
meter and the local gas undertaking should be
consulted to determine the suitability of the meter and
gas supply to meet existing and additional demands
for gas.
The installation should be made in accordance with
the requirements of the Gas Safety (Installation &
Use) Regulations and all other regulations and Codes
of Practice
In particular, before connecting the boiler, ensure that
the gas supply has been purged of air and a manual
valve for isolation of the boiler is fitted in an accessible
position, readily identifiable, adjacent to the boiler.
The gas supply should be supported adequately.
For large single and multiple boiler installations
consideration should be given to the installation of
additional gas meters to assist in the monitoring of
boiler performance.
Attention is drawn to the need for adequately sized
pipework according to the maximum gas demand for
multiple boiler installations and each boiler shall be
provided with an isolating valve so that it is possible to
isolate the boiler from a common gas supply for
maintenance purposes. The gas train is fitted with a
low-pressure switch, which is set to operate at a
minimum gas pressure of 13mbar.
Boiler Controls
The operation of the boiler is under the control of it's
own control box, boiler thermostats, 2 air pressure
switches, gas pressure switch and overheat
thermostats.
In addition, the boiler should be controlled by a time
switch, frost thermostat, pump overrun facility and, for
multiple boiler installations, a boiler sequence
controller. The boiler can be controlled externally by
removing link D to G and providing a switch across
these terminals to control the boiler.
The high limit thermostat and burner lock out signals
can be picked up from terminals marked remote
indication. These are volt free contacts.
See boiler wiring diagram.

SECTION 5 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 12 DERWENT COMPACT PLUS - CONDENSING
Potterton Commercial Customer Commissioning
Check List
The items listed below have been put together as a
guide to what actions should be completed before the
commissioning of a boiler takes place.
1 Site access available for persons carrying out
the proposed work.
2 Site Managers/Personnel aware that work will
be taking place.
3 Boilers correctly erected and cased.
4 Risk Assessments carried out on possible risks
which may effect the persons carrying out the
proposed work.
5 Site wiring complete to boilers.
6 Boilers filled & vented.
7 Controls connected, operable and calling for
heat.
8 Sufficient system heating load available to run
the boilers in order to complete combustion
checks.
9 All system pumps operational and available.
10 Gas supply completed, purged and ready for
use.
11 Flue system complete, adequate and fully
functional.
12 Permanent ventilation complete and adequate.
13 All safety systems fitted and fully operational
(e.g. safety valves, fuel shut off devices, flue
fans interlocked, etc.).
14 Safe working environment provided.
Contravention of Regulations
PLEASE NOTE THAT SHOULD ANY ITEMS BE
INSTALLED ON A TEMPORARY BASIS, E.G.
VENTILATION, FLUES ETC, THEN THE
COMMISSIONING ENGINEER WILL NOT BE ABLE
TO COMMISSION THE BOILER
Commissioning
IMPORTANT: The boiler must be commissioned
following completion of installation. Operation of
an uncommissioned appliance may cause injury
to personnel and damage to the boiler/burner unit
and could invalidate the manufacturer's
warranties.
Commissioning should only be carried out by
personnel approved and competent to do so. This
facility is available from Potterton Commercial Service
Offices at the addresses as listed on the back page of
this manual.
Before commencing to commission check the
following.
1 Electrical supply is of correct voltage and
polarity and earthing is available with
certification that all electrical checks have been
carried out.
2 Gas supply is tested for soundness and purged
of air. Ensure that the burner is suitable for
connected gas supply and pressure.
3 Test for gas soundness of gas trains.
4 Appliance gas cocks are all turned off.
5 Gas supply is turned on at the meter.
6 Boiler and system are filled with water and
operating pressure is within appliance range.
7 Flow and return valves are open.
8 Any external controls and the on/off switch are
in the “ON” position.
9 The circulating pumps are operational. Check
that the pump is scheduled to run and not on
pump overrun if the boiler has previously been
fired. Check that any flow proving interlocks are
functional.
10 Check that the high limit thermostat has not
tripped by pressing the green reset button
underneath the hexagon cap nut on the fascia.
11 Ventilation is adequate and, in the case of
mechanical ventilation systems, operation of
the boiler is inhibited unless the ventilation fan
is proved.
12 On mechanically assisted flue systems the
operation of the boiler plant should be inhibited
unless the mechanical flue system is
operational and flow proved.
13 The safety valve should be checked to ensure
that it is the correct size and pressure.

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 5
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS - CONDENSING PAGE 13
14 The cold feed and open vent sizes should be
checked
Following completion of the above checks the burner
should be commissioned. Typical combustion figures
are detailed below. The combustion figures, etc.
should be completed on the commissioning form
provided at the back of this manual and returned to
Potterton Commercial at the address on the back
page.
Commissioning figures should be taken with the boiler
at high fire and a flow temperature of 80°C. The
combustion measurements should be taken in the
secondary flue at a minimum of 600mm above the
draught diverted.
GAS CO2-See Table 3
CO - 0 - 50 ppm
Flue Gas Temp - See Table 3
Check and ensure that the boiler cable
connections internally of the boiler are connected
in accordance to the drawing below.
Ignition transformer - gas
pressure switch,
connector 6 way
Thermostats
cables
Ignition
connector
Burner security
thermostat
connector
Complementary gas
valve connector
Thermostat
pocket
Main valve 2 stage,
connector 9 way
Ionisation
connector
1 Overheat Thermostat
2 Thermometer
3 Control Thermostat
4 Tube Ø 6 mm?
5 Control Sensor

SECTION 5 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 14 DERWENT COMPACT PLUS - CONDENSING
Control Panel
The CE 100 module provides the following
functions:
-Operation at 1st Stage
-Detection of boiler overheat, ionisation
probe fault
-Ability to restrict max boiler temperature
using jumper at back of module
-Indication of the operation mode of the boiler
-Operation of 2nd Stage operation.
The CB 120 module provides the following
functions:
1. Reset Button
2. Overheat Thermostat
3. Overheat Indicator
4. Lockout Indicator
5. Mains Supply Indicator
6. On/Off Switch
7. Override button for Safety Checks
8. Override Thermostat (Set fully to the
right((maximum position)) allowing control by
the 1st Stage and 2nd Stage thermostats)
9. 6.3 Amp Fuse
10. Boiler Thermometer
Gas Assembly
(8 Section Model Shown)
The Gas Assembly is pre-set at the factory ready
for use at high and low conditions.
The 4 Section model has one main valve, the 6 &
8 section have one main gas valve and one slave
valve.
The main gas valve has a two-stage governor for
high and low load (left valve).
The slave gas valve has single stage operation
only and its governor is pre-set at the factory.
The governor has a yellow cover and the setting
up is shown below.
Set-up
For fine adjustment of the gas valve on
commissioning in order to obtain the correct
Pum
p
Switch
(
Not Used
)
Pump Indicator
Li
g
ht
Boiler Temperature
Control Thermostat
Green Indicator Light
Showing 1st Stage Run
(If light flashes indication of
overheat fault)
2n
d
Sta
g
e Thermostat
2n
d
Stage
Indicator Light
CE 100
CB 120
1
2
3
4
8
7
65
10
9

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 5
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS - CONDENSING PAGE 15
burner manifold pressure the following procedure
should be followed:
-Loosen the screw on the burner manifold
and connect a manometer and check the
pressure available to the data in the
technical data table.
-Take off the yellow governor cover.
-Set up the valve to achieve the figures for
high and low load.
(Adjusting Full Load)
(Adjusting Low Load)
Adjusting the Air
Airflow flow control (CO2 Control at high load)
The CO2 setting for full load is pre-set at the
factory. The installer has to verify the CO2
content by taking a reading in the flue between
200mm and 300mm from the top of the flue
connection. The Technical Data Table indicate
the range acceptable. The air can be re-set by
the damper on the inlet to the fan and altering the
securing positioning on this damper.
Arrangement shown on the next page.
Air flow rate control at high load by device
directly on the damper. The hole position defines
A - Adjusting screw for full load
B - Adjusting screw for low load
C - Cover
A
B
C

SECTION 5 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 16 DERWENT COMPACT PLUS - CONDENSING
the right damper positioning.
Model 4 6 8
Hole Position 3 3 6
Low Load Control & Set-up:
The control and setting is carried out as high fire
setting. The low fire set-up is achieved by the
adjustment of the rheostat which is located at the
inner side of the front panel. Rotating the
rheostat allows the correct resistance to be
obtained as shown on the table below.
Measuring the resistance is carried out by an
ohm meter connected as shown below:
Model 468
Resistance
Ohm
560 270 100
The resistance tolerance is about 5 Ohms
IMPORTANT: The boiler/burner units are
manufactured in accordance with ISO 9002. A
condition of the supply of the appliance for
compliance with this Quality Assurance plan is
the return of the appliance commissioning report.
Important – Safety
In the U.K. it is a legal requirement that when working
on gas appliances the engineer must be CORGI
registered. The manufacturer cannot be held
responsible for any consequential damage, loss or
personal injury as a result of customers failing to
follow these instructions, or as a result of misuse.
Emergency Instructions
The burners are designed and constructed to meet all
of the essential requirements of the GAS APPLIANCE
DIRECTIVE 90/396/EEC and under normal
circumstances should not give occasion to any
hazardous conditions. If such a condition should occur
during commissioning or subsequent use of this
product, be it a fault of the boiler or of any instrument,
machine or service in the proximity of the burner then
the GAS and ELECTRICITY supply to the burner
should be IMMEDIATELY ISOLATED until such time
that the fault has been investigated and rectified.
IMPORTANT After each adjustment, gas flow rate
and flue gas analysis should be re-checked.
ALWAYS Use approved test equipment (continually
monitoring electronic equipment is recommended).
NEVER Rely on a visual inspection of the flame as a
guide to combustion quality.
Following/during commissioning of the burner unit the
following additional checks should be carried out.
1 Operation of the control, high/low and limit
thermostats should be checked for correct
2 The flue draught available at the appliance flue
outlet should be checked under all operating
conditions (hot and cold) and should be within the
boiler operating parameters, see Table 3.
3 The fuel supply to the appliance should be
isolated and the burner operated to ensure safety
shut down and lockout of the burner on flame
failure.
4 Shut down of the boiler plant by external controls
does not cause a hazardous condition and pump
overrun is provided to remove residual heat from
the boiler.
5 Following commissioning the boiler overheat and
control thermostats should be set to the required
operating setting.
6 Following completion of commissioning the
soundness of all automatic fuel valves should be
checked for leakage.
Additional Checks
Where possible, the system should be checked to
ensure that following purging of air there is no raw
water make-up. In particular, when the system is
operated in the hot condition, there should be no
discharge of water from the safety valve, open vent or
cold feed tank overflow that would otherwise lead to
unregulated raw water make-up when the system
cools down.
Pre-Lighting
Before attempting to light the boiler start the
circulating pump and check that it is scheduled to run
Hole No 1

POTTERTON COMMERCIAL PRODUCTS DIVISION SECTION 5
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
DERWENT COMPACT PLUS - CONDENSING PAGE 17
and not on pump overrun if the boiler has been fired
previously.
Check that the pilot gas cocks and electrical supply
are turned off.
Set the boiler control thermostat to the required
position and the time clock to the ‘ON’ position. Check
that the high limit thermostat has not been tripped by
removing the hexagon cap nut and pressing the
button beneath it.
Start the boiler by switching on the main isolator and
the on/off switch on the boiler control panel fascia and
the boiler will attempt to light. After a delay (pre-purge
time) of approximately 40 seconds the ignition spark
should be heard and after 5 seconds the control box
should lock out.
If the ignition spark is not detected or the control box
does not lock out see Fault Finding
Commissioning Live Run
1 Turn on the appliance isolation valve.
2 Check the inlet pressure, which should be at least
20mbar, on the inlet test pressure point and note
the value.
3 Close the pilot supply gas cock and check that the
pilot pressure is zero and not moving.
4 Turn on the electricity supply at the main isolator
and at the on/off switch on the control panel
fascia, (ensuring that time clocks and any other
external controls are made or are in the ON
position) also turn on the pilot isolating valve.
5 Approximately 40 seconds (pre-purge time) after
switching on the ignition a spark should appear
followed by ignition of the pilot burner. If the pilot
flame is not established the control box will
lockout in approximately 5 seconds..
6 The control box may be reset after a delay of five
seconds by pressing the reset button on the
control panel and the red light will go out. When
the pilot flame is established check the gas
pressure on the gas manifold pressure nipple and
adjust the regulator if necessary (located on the
gas valve). Turn off the pilot check valve and pull
off the ionisation probe and check that the pilot
and main burner shuts down.
7 Re-connect the ionisation probe and tune on the
pilot check valve and the pilot burner will relight
followed 10-15 seconds later by the main gas
burners.
8 Observe the main gas flame through the viewing
port above the pilot burner, the flames should be
blue and well defined ‘V’ shaped flame. Then
check the main gas manifold gas pressure and
adjust to give correct burner pressure
9 For high/low operation the high fire rate must be
set first.
With a pressure gauge fitted to the burner
manifold, turn the boiler on and set the gas valve.
Before any adjustment can be made the yellow
cap must first be removed.
Adjust the high fire adjustment screw using an
8mm spanner to turn the adjustment screw,
clockwise to increase and anti-clockwise to reduce
until correct high fire burner pressure is reached.
The low fire rate can now be adjusted by adjusting
the low fire adjustment screw using a screwdriver
(clockwise increases and anti-clockwise reduces
the low fire burner pressure) until a low fire burner
pressure is reached.
Operate the boiler at high and low fire checking
that the burner manifold pressure is correct and
that the flame is stable and blue.
10 Test the gas connection between the ignition valve
and the pilot burner for soundness with a soap
solution or other approved method and seal any
leakages. Switch off the electrical supply and
check that the burner has extinguished. Remove
the pressure gauge from the burner manifold and
replace the sealing screw.
11 Check the reliability of ignition of the boiler by
switching the boiler off using the burner on/off
switch on the boiler control panel. After two
minutes turn the switch back on. The boiler will
now relight. Check that the pilot has a stable
flame and that the main burners light smoothly.
12 With the boiler switched on test for soundness
between the gas valve and the burner manifold
with a soap solution or any other approved
method and seal any leaks.
13 Turn the appliance isolation valve off. The main
and pilot burners should go off. The boiler will
attempt to relight. Check that the ignitor starts
and that the boiler locks out.
Gas Valve Arrangement
Single stage
valve
DO NOT adjust
Pressure
switch
Valve
Adjustment
under Cap

SECTION 5 POTTERTON COMMERCIAL PRODUCTS DIVISION
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
PAGE 18 DERWENT COMPACT PLUS - CONDENSING
Fig. 21A – Honeywell VR4601Q Gas Valve
Ionisation Current Check
Switch the boiler off at its on/off switch and at the
main isolator. Connect a micro ammeter into the
ionisation cable in between the electrode and cable.
Switch on the main isolator and the burner on/off
switch and after 15 seconds the ignition spark should
be heard followed by lighting of the pilot burner. The
micro ammeter should read approximately 3 - 4µA.
Switch off the main isolator and the on/off switch and
remove the micro ammeter connections.
Ventilation Checks
For boiler houses with natural ventilation, the area of
the grilles should be checked against the notes given
on Ventilation in Section 3.
For boiler houses with mechanical ventilation, the
suitability of the ventilation and extract system should
be checked against the notes given on Mechanical
Ventilation in Section 3.
In addition, the installer must check that it is not
possible for the boiler to operate if either the
ventilation or extract fans are not running.
THE BOILER SHOULD NOT BE OPERATED
WITHOUT ADEQUATE VENTILATION.
Operation Of Ancillary Controls
After lighting the boiler the operation of the above
mentioned controls, eg. clock and thermostats, should
be checked.
To Shut Down Boiler
1. Temporarily - Switch the on/off switch to "OFF".
Switch off the electrical supply.
2. Long Periods - As above but in addition turn off
the service cock at the gas meter.
Boiler Maintenance
It is essential for efficient and trouble free operation
that the boiler plant is regularly maintained. This must
be carried out by qualified and experienced engineers
and in the case of gas fired appliances attention is
drawn to the mandatory requirement of CORGI
(Confederation of Registered Gas Installers)
registration of personnel undertaking work on these
appliances. This facility is available from Potterton
Commercial Division, details are available from
Regional Offices listed on the back page back of this
manual.
Boilers should be serviced and re-commissioned as a
minimum on an annual basis but frequency may
depend on usage and application of the boiler.
It is strongly advised that a maintenance contract be
entered into with Potterton Commercial Division to
ensure that the boiler/burner unit is correctly and
properly maintained.
WARNING Isolate the electrical and fuel supplies
before attempting any maintenance work.
Following completion of maintenance on the boiler the
boiler should be re-commissioned.
Boiler Cleaning
At every service visit the boiler should be cleaned as
detailed below and the soundness of the gas control
assembly must be checked. The boiler should be fully
re-commissioned as described below with attention
also paid to -
1 The effectiveness of natural and mechanical
ventilation and in particular the safe operation of
an air flow switch on a mechanical ventilation
system.
2 That the chimney system is sound and
adequately evacuating the products of
combustion and that there is no spillage of flue
products.
3 That the burner gas pressure is correct and that
the boiler is still on rate.
4 That the low pressure switch on a booster
Cap
Adjustment screw for
High Fire
Valve Adjustment under
Cap